1. Field of the Invention
The present invention relates to a sliding member having high strength and excellent heat resistance, abrasion resistance and oxidation resistance. The sliding member is suitable for making a brake shoe, a brake lining, a brake pad, a bush, a thrust washer, a piston ring, vanes, rotors and sleeves of pumps, a bearing for a high temperature application and the like for an aircraft, a racing car and so on.
The sliding member of the present invention can be applied to both of a dry type friction member and a wet type friction member. Further, the sliding member of the present invention can be made into a sliding member having a low friction coefficient and excellent anti-seizure properties under a dry sliding condition and being applicable to a mechanical structural body, thereby contributing to reduce the frictional loss thereof.
2. Description of the Prior Art
A sliding member used in a brake shoe component member the like for an aircraft, a racing car and so on especially requires heat resistance and abrasion resistance. On the contrary, since a sliding portion of a mechanical structural body has poor anti-seizure properties, the sliding portion is usually used under an oil lubrication condition. As for a sliding member used under a dry condition, a sintered material impregnated with an oil, a copper sintered alloy and a carbon material have been well known. As for the carbon material, the following carbon materials have been used, i.e., a carbon material made by burning and solidifying a carbonaceous powder and the other carbon material made by sintering a carbonaceous powder at a high temperature to graphitize the carbonaceous powder.
Recently, carbon fiber reinforced carbon has been provided for the above-mentioned applications, and is said to be a material improving the strength of the conventional carbon materials. According to Japanese Unexamined Patent Publication (KOKAI) No. 206351/1988, this carbon fiber reinforced carbon is produced by impregnating a liquid carbonaceous material, such as tar, pitch and thermosetting resin, which works as a binder into carbon fiber which works as a reinforcement and which has been carbonized or graphitized and further subjected to a surface treatment like oxidation. Then, the resulting binder impregnated carbon fiber is burned in an inert gas atmosphere. If necessary, the resulting sintered product is graphitized thereafter.
Since the carbon fiber reinforced carbon thus produced uses the liquid carbonaceous material as the binder, volatile substances are generated by the decomposition of the liquid carbonaceous material during the burning, thereby forming pores. Accordingly, the boundary adhesion between the reinforcement and the binder deteriorates, and the density of the product decreases. Consequently, the product is inferior in the strength and the abrasion resistance.
To solve the above-mentioned problems, the pores of the product have been repeatedly filled with a liquid impregnant working as a binder, and the product has been repeatedly re-burned to decrease the porosity. However, in spite of these complicated processes, the product thus obtained has been still porous. In addition, these complicated processes have resulted in the increasing manufacturing cost.
Further, the above-mentioned conventional carbon fiber reinforced carbon suffers from a low friction coefficient (.mu.) especially under a low load.
Furthermore, through the above-mentioned conventional carbon fiber reinforced carbon has been known to be superior in the anti-seizure properties, it is seized at the load of 50 to 75 kgf/cm.sup.2 which is as much as 3 to 4 times that of steel for a structural application under a dry condition. In addition, since the carbon fiber reinforced carbon only exhibits the friction coefficient (.mu.) of 0.2 to 0.5 under a dry condition, it is not a material of a low friction coefficient, nor a suitable material for a sliding portion of a mechanical structural body.